Geography Coastal Processes

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Transcript of Geography Coastal Processes

Harry Chapman Coastal processes Palm Beach task Part 1 - Coastal processes Coastal processes: Erosion Wave cut platform - cliff Long shore drift at Palm Beach Erosion at Palm Beach Palm Beach is a northern beachside suburb of Sydney, in the state of New South Wales, Australia. Palm Beach is located 41 kilometres north of the Sydney central business district, in the local government area of Pittwater Council, in the Northern Beaches region. Palm Beach sits on a peninsula at the end of Barrenjoey Road, between Pittwater and Broken Bay. Wave cut platform annotated Coastal processes: Deposition - Tombolo Long shore drift was evident during our visit to Palm beach. This was seen through the subsequent formation of the tombolo which joins Barrenjoey head to South Palm Beach. The Long shore drift was caused by the various sources of the material in the sea. The material had been:- eroded from cliffs.- transported by long shore drift along the coastline.- brought inland from offshore by constructive waves.- carried to the coastline by rivers.At Palm beach as well as many other beaches waves approach the coast at an angle because of the direction of the prevailing wind. The swash of these waves carry material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90 degrees. This movement of material is called transportation.Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift.

How the tombolo was formed?

The Palm Beach tombolo was formed over 12,000 years ago when the wave refraction patterns from two landmasses caused sand and other materials to be deposited between them, eventually forming a bridge between Barrenjoey island and the south Palm beach headland. Coastal processes cont... Sketch of dune zone The main coastal processes seen at Palm Beach were: Erosion. The process by which the surface of the earth is worn away by the action of water, winds and the waves.

These was evident through the subsequent formation of the wave cut platform and cliff faces.

Other forms of erosion are caused by destructive waves which erode the coastline in a number of ways:Hydraulic action. Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.Abrasion. Bits of rock and sand in waves grind down cliff surfaces like sandpaper.Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

The wave cut platform at Palm beach was formed due to the above processes. When cliffs are being worn away, the processes of weathering and erosion only act on the parts of the cliff that are above the level of the beach. Once the cliff has been worn down to the same level as the beach, the ability of the sea to continue to erode the remaining rock becomes much reduced. Under the right conditions the continuous erosion and landward retreat of the cliff line produces a wide, flat, area of rock, often only visible at low tide, looking as if the foundations of the cliff have been exposed. This is called a wave cut platform. The effects of erosion at Palm beach were seen throughout the day. We came to see the ‘honeycomb’ formation of rocks exposed at the south headland due to prevailing winds as well as the breaking down of rock and sediment which was evident toward the bottom of the rock platforms. I also wanted to highlight incidences of erosion seen in the past at Palm beach that were temporarily very destructive. As seen in the below images, tidal actions such as king tides and large surf have washed away up to 3m of sand from the beach in previous years leaving a cliff like structure seen in image 2. Also, it is seen that the ocean and waves are washing away the bottoms of the sand dunes destroying plant life and vegetation. Palm Beach represented by its absolute location is 33°36′04″S 151°19′18″E. It is roughly 2.6 km² in size and contains both the ocean side of Palm beach and the bay side of Pittwater. Longshore drift was evident at Palm beach due to the direction the sediment faced along the beach. Also, field tests such as the ‘tennis ball test’ were implemented by placing a tennis ball in the water and observing its movements up or down the beach. We know that longshore drift has occurred at Palm beach as it has formed the tombolo over 12,000 years ago which still exists today. Part 2 - Human impacts Part 3 - Management strategies The sand dunes present at Palm beach are a key area for the introduction of new species. The dunes are surrounded by bushland which highlights the great biodiversity of the plant life. From our field work we could see approximately 5 up to 12 different species of plants as we progressed through the dunes. The introduction of these new species at Palm Beach help to sustain plant life as some plants have adapted to the conditions. For example, many of the plants present at the ocean side of Palm beach have adapted to the high salinity and wind with poor soil nutrition. The introduced species we encountered were pig face, Norfolk pines, biteau bush, lantanna, asparagus fern and date pine as seen below. Throughout the visit to Palm Beach we were consistently exposed to the management strategies implemented to reduce the damage done to native plants and animal life. Things that were seen were wired fences containing plant life, waste bins, signage and light house maintenance. Waste/pollution Pollution at Palm Beach effects the biodiversity and sustainability of the plant and animal life in surrounding areas. General rubbish and waste left behind from visitors has a huge effect on animal and plant life. As you can imagine, certain species try to eat this rubbish often resulting in their death. By their deaths, other animals who rely on them as prey are effected as food becomes harder to find. This pollution throws ecosystems around often effecting more than just one species. Other forms of pollution from boats, cars etc. also have an effect. With emissions from their usage emitted into the surrounding area fish life are affected from things such as oil spills from boats. From cars, the air becomes dirtier effecting bird life etc. Creation of recreational areas From the image above it is evident that land clearing was in great affect to provide the recreational areas present today. The golf course would have required a great deal of land clearing which may have resulted in the destruction of natural habitats of animals. Also, land clearing would have been used to make areas for car parks to provide for the growing tourist attractions as well as making room for parks and playgrounds present above. Fences at Palm Beach are used to enclose plant life. By doing this, it limits the intrusion of animals and humans into the environment and effectively sustains the ecosystems involved in the plant life. Roads at Palm Beach direct cars and other modes of transport to travel along lines that are protected and will not effect the natural plant life. In previous years, a caravan park was present on the Pittwater side and grass and plant life were being destroyed form constantly being run over. Roads prevents such destruction. Paths also limit erosion due to rainfall. Fences/paths/roads Signs The signs present at Palm Beach show clearly the efforts made to create a sustainable environment for aquatic and terrestrial creatures. The signs at Palm Beach highlight the dangers present as well as providing details and background information on the area. The signs work to inform the public and warn them of the boundary lines in place in order for the ecosystems in Palm Beach to be sustainable. They often display fines for those breaking the law, provide alternatives, educate the public as well showing past and previous events in the area to warn the public of such dangers that have or are still present. The management strategies implemented at Palm beach generally work helping to sustain the animal and plant life. Signage, fences and pathways more often than not deter humans from entering dangerous or endangered areas whilst roads keep traffic away from these areas limiting the destruction to wildlife. However, management strategies implemented are also ignored by some which means that tougher laws and regulations are often needed especially needed for the overall sustainability of the Palm beach area.Overall, the management strategies at Palm beach are environmentally sustainable as they often use natural materials such as the sandstone from the surrounding area and timber and wood from local industries. This effectively makes the management strategies economically sustainable as well.